The present invention relates to a sintered ceramics and a manufacturing process thereof, particularly, to a sintered ceramics of alumina-titanium nitride (Al.sub.2 O.sub.3 -TiN) type which has conventionally been produced by pressing at a high temperature such as hot pressing- or HIP process, now according to the present invention being capable of being produced by a powder metallurgical process at a low cost.
It has been known that the Al.sub.2 O.sub.3 -TiN type ceramic tools obtained by sintering a mixture of 5-40% by volume of TiN and the balance of Al.sub.2 O.sub.3 by the hot pressing process or by the hot isostatic pressing process (HIP process) show a very high resistance to oxidation and crater formation thus that those are outstanding as cutting tools (Japanese Patent Application Open-laying No. 50-89410). However, the hot pressing process is not suitable for mass production since a ceramic plate thereby is pressformed, sintered in a graphite die then being cut and machined by diamond grinding wheel, resulting in a high cost for the commercial production. On the other hand, it is necessary for the HIP process to use gas (usually argon) as a pressure medium, thus the HIP sintering must be applied either after coating of the surface of the body to be sintered or after a presintering step up to a relative density of not less than about 95% of the theoretical density, which makes this process difficult to be applied commercially.
Accordingly, the object of the present invention is to provide a novel sintered ceramics and a novel manufacturing process thereof which can eliminate the drawbacks of the prior art.
A further object of the present invention is to provide a novel sintered ceramics which can be sintered without applying the hot pressing or the HIP process and a novel manufacturing process thereof.
A still further object of the present invention is to provide a novel sintered ceramics which can be produced at a low cost and is suitable for the commercial mass production and a manufacturing process thereof.